Gas sensors can be used for measuring a concentration of a gas (e.g., oxygen, carbon dioxide) in a gas flow through an engine in a vehicle. For example, a gas sensor may be positioned in an intake manifold of the engine for measuring gases that are entering a combustion chamber and/or in an exhaust passage of the engine for measuring gases that are contained in exhaust leaving the combustion chamber. Such gas sensors located in the intake manifold or exhaust passage can be utilized for determining an accurate air-fuel ratio, for example, and engine operating parameters (e.g., sparking timing, fuel injection, etc.) may be adjusted accordingly thereby improving or maintaining engine performance.
In order to protect a sensing element of the sensor from debris such as soot, a sensing element of the sensor may be covered by a shield that is perforated so that the gas flow may reach the sensing element. Further, in some examples, the gas sensors may be operated at high temperatures (e.g., 700-800° C.). When the gas sensor is positioned in certain locations, fuel vapors may pass through the sensor shield and interact with heating elements of the sensor to ignite. The ignited constituents may then interact with other gasses or substances in the vicinity of the sensor, thereby degrading engine operation.
The inventors herein have recognized the above issues and have devised an approach to at least partially address them. In one example, a method for an engine in a vehicle is disclosed. The method comprises delivering a fuel to a cylinder of the engine, combusting the fuel with a gas flow through the cylinder that enters the cylinder from an intake manifold and leaves the cylinder through an exhaust passage, and generating an indication of oxygen concentration in the gas flow via a heated gas sensor, the gas sensor having a porous metal shield without perforations.
In one embodiment, the fuel may be gasoline and the gas sensor may be positioned in the intake manifold of the engine. Due to a high operating temperature of the sensor, fuel vapor in the intake manifold may ignite in the vicinity of a sensing element of the sensor. By using a porous metal shield without perforations to cover the sensing element, the gas flow in the intake manifold can still permeate the shield so that an indication of gas concentration can be generated and, if fuel vapor in the gas flow is ignited in the vicinity of the sensing element, flame propagation can be retarded by the shield and contained to within the shield.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.